Probing the Genetics of Intelligence

Some geneticists are skeptical of a project that will analyze the DNA of high-IQ individuals to identify genetic variants related to intelligence.

By Dan Cossins | May 15, 2013

Researchers in ChinaWIKIMEDIA, JEFF KUBINA will scour the genomes of 1,600 super-smart people in an attempt to find common genetic variants associated with intelligence, reported Nature. But some geneticists argue that the sample size remains too small, and intelligence too complex, for the study to produce any meaningful conclusions.

“If they think they’re likely to get much useful data out of this study, they’re almost certainly wrong,” geneticist Daniel MacArthur of the Massachusetts General Hospital told Nature.

Previous attempts to identify intelligence-related variants in the general population have failed, but behavioral geneticist Robert Plomin of King’s College London has now teamed up with the BGI (formerly the Beijing Genomics Institute) in Shenzhen to sequence DNA samples he collected from a cohort of Americans who were recruited to the Study of Mathematically Precocious Youth (SMPY) group in the 1970s. The plan is to compare the genomes of these people, who have an average IQ of over 150 (compared to 100 in the general population)—and those of other highly intelligent individuals recruited by the BGI—with those from 4,000 controls, who should have a range of IQs.

But MacArthur pointed out that if the genetics of intelligence are as complicated as those of schizophrenia, or even height—in which the effects of thousands of variants combine to influence the trait—the researchers would need at least 10,000 cases and the same number of controls to detect influential variants. And if it turns out a few rare mutations produce extreme intelligence, they will be even less likely to find them in such a relatively small sample.

As the cost of sequencing continues to plummet, such larger sample sizes could one day become a reality, University of Queensland geneticist Peter Visscher told Nature. Even so, he insists, the goal of predicting intelligence from DNA is far fetched. “Even for human height, where you have samples [from] hundreds of thousands [of people], the prediction you’d get for a newborn person isn’t very accurate,” said Vischer. “That will be true for IQ for a long time to come.”

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Long ago, David Hume proposed that it is a logical fallacy to conclude that a correlation means a cause and effect. Simply correlating genetic variants with high IQ scores does not mean that the genetic variants produce the high IQ scores.

Hume went so far as to say that you cannot logically conclude the sun will rise in the east tomorrow simply because it has done so every day in the past.

The hope of associating intelligence with specific genes is utterly silly, simply because there isno utile deinition of intelligence!

All IQ tests measure is a person's ability to learnwhat is taught inhisown specific culture, eventhough he has learned nothing about wha people learn in other cultures. What has this got to do with intelligence,whatever intelligenceis???

This point was broughthome to me many years ago, as a result of IQ tests conducted inIsrael, whichcompared native Israeli kids withkids who were Jewish new immigrants from Yemen. Both groups of kids were shwn a simple drawing of a boy's face with only one eye, and asked what was missing in the drawing. Native Israeli kids immediately said theboy was missing an eye. The Yemeni kids said he was missing his side-locks!

Does that mean that the native Israeli kids had a higher IQ? of course, not! The Yemeni kids came from a country where an eye diseae that caused people to lose sight in one eye, which deteriorated to the point of completely closing, was very common. So there was nothing unusual about a drawing of a boy's face with only one eye! Those Jewish Yemeni kids, however, also came from a strictly religious Jewish culture, where all boys had to grow side-locks!

I've since then become aware of anothe, veryr interesting study done in Australia, that tried to compare the intelligence of white kids, with that of aboriginee kids of the same age. The white kids scored much higher on questions about material that was taught in school. But then the kids were given adifferent kind of test, where thewhite kids failed completely, while the aboriginee kids did very well. The kid were shown a large square drawn in the sandand divided into 16 identical small squares. A different combination of various pebbles and sticks was placed in a specific arrangement in each square. The kids were allowed to view the arrangements for a brief period of time. All the object were then removed, and the kids were asked to place them back in the exact original arrangements they had seen. The white kids were ubable to do it, but the aboriginee kids aced through the test. In the environment where aboriginee kids live, it is extremely important to pay very close attention to such details, which the white kids were never even trained to notice!

IQ tests obviously have nothing to do with intelligence, and do not teach anyone what the term intelligence even means. If scientists wish to search for something, they must first verypreciselydefine wha tthisthing is! This has never been accomplished, or even attempted, for a concep l ike intelligence!

If your rare mutation was obtained by accident, how did the accident intelligently confer increased intelligence? Or did it unintelligently or non-intelligently confer it, meaning all intelligence may have evolved by accident? Try in other words to explain the mechanism that creates what it otherwise neither has nor uses.